Remove built-in search-engines in Firefox Nightly

I don't use the default Firefox search-engines, so I like to be able to delete all the Amazon, Twitter, Google nativelly installed on every Firefox version. Using current and beta version of Firefox, I am able to remove built-in search-engines on the Android version, simply from the add-ons manager and disable the search-engine.

However, on the last Nightly build, the search-engines can not be found in the add-ons manager. My phone is not rooted, so I'm not able to directly set the search-engines list by editing the files or removing it through the search-engines list. Can't find a property in `about:config` either...

I don't use the default Firefox search-engines, so I like to be able to delete all the Amazon, Twitter, Google nativelly installed on every Firefox version. Using current and beta version of Firefox, I am able to remove built-in search-engines on the Android version, simply from the add-ons manager and disable the search-engine.
However, on the last Nightly build, the search-engines can not be found in the add-ons manager. My phone is not rooted, so I'm not able to directly set the search-engines list by editing the files or removing it through the search-engines list. Can't find a property in `about:config` either...

Chosen solution

You can still disable the search engines if you have root access to your device. Specifically, you need to pull and modify the file search.json. On my device, I have:

You need to take the "_hidden" flag and change it to true. Do this for all of the search engines to hide all of them. Or, frankly, just delete everything under engines. Then, upload the file back and restart firefox with a command like:

As a slight editorial note, it's dumb that we have to do this by hand. Either we should be able to disable things under Settings->Customize->Search settings or we should have some way of turning things off in about:config. While I understand that removing menu items that cause too many support issues, completely removing the option even from about:config is counterproductive.

You need to take the "_hidden" flag and change it to true. Do this for all of the search engines to hide all of them. Or, frankly, just delete everything under engines. Then, upload the file back and restart firefox with a command like:

As a slight editorial note, it's dumb that we have to do this by hand. Either we should be able to disable things under Settings->Customize->Search settings or we should have some way of turning things off in about:config. While I understand that removing menu items that cause too many support issues, completely removing the option even from about:config is counterproductive.

You can still disable the search engines if you have root access to your device. Specifically, you need to pull and modify the file search.json. On my device, I have:
adb pull /data/data/org.mozilla.firefox/files/mozilla/rbn69ru0.default/search.json
Now, by default, this file doesn't format everything nicely, so you can use something like
http://jsonformat.com
In order to clean things up. In any case, you'll see bits such as
"_id": "[app]/bing.xml",
"_name": "Bing",
"_hidden": false,
"description": "",
"__searchForm": "http://www.bing.com",
You need to take the "_hidden" flag and change it to true. Do this for all of the search engines to hide all of them. Or, frankly, just delete everything under engines. Then, upload the file back and restart firefox with a command like:
adb push search.json /data/data/org.mozilla.firefox/files/mozilla/rbn69ru0.default/
Until an application restart, the changes won't be seen.
As a slight editorial note, it's dumb that we have to do this by hand. Either we should be able to disable things under Settings->Customize->Search settings or we should have some way of turning things off in about:config. While I understand that removing menu items that cause too many support issues, completely removing the option even from about:config is counterproductive.

Helpful Reply

The root solution is useful but not everybody is root and this search engines re-ordering function seems to be pretty basic. However, I'm sure there is a lot of reasons for having remove it since pas versions.

The root solution is useful but not everybody is root and this search engines re-ordering function seems to be pretty basic. However, I'm sure there is a lot of reasons for having remove it since pas versions.